<!DOCTYPE html>
<html>

	<head>
		<meta charset="UTF-8">
		<title></title>
		<style type="text/css">
			.main div {
				width: 100px;
				height: 100px;
				border: 1px solid red;
				display: none;
			}
			
			.main {
				width: 100%;
				height: 100%;
				border: 1px solid blue;
			}
			
			@media only screen and (max-width:1000px) {
				#sj {
					display: block;
				}
			}
			
			@media only screen and (min-width: 1200px) and (max-width: 1240px) {
				#pb {
					display: block;
				}
			}
			
			@media only screen and (min-width: 1241px) {
				#pc {
					display: block;
				}
			}
		</style>
	</head>

	<body>
		<div class="main">
			<div id="sj">
				这是手机哟~
			</div>
			<div id="pb">
				这是平板哟~
			</div>
			<div id="pc">
				这是pc端哟~
			</div>
		</div>
	</body>

</html>